The present invention relates to alignment devices for radiant energy beams. It is particularly useful with respect to manipulatable laser beams, such as are used as laser surgical scalpels, and is therefore described below in connection with that application.
As is well known, a laser beam can be focussed to a very small spot size (e.g. 100 microns or less in diameter) to produce an extremely hot concentration of light energy. At laser wave lengths (e.g. 10.6 microns), the laser energy is almost completely absorbed by body tissue and therefore a focussed laser beam may be used to cut through most types of tissues by burning or vaporizing. One of the important advantages of using a laser beam for this purpose is that it can make very clean and fine cuts while minimizing damage to tissues outside the cutting lines. Also, the laser beam readily coagulates capillaries, small veins and small arteries, thereby minimizing loss of blood and keeping the working area clean. Because of these advantages, manipulatable laser beams are increasingly being used as surgical scalpels.
One problem, however, in using laser beams as surgical scalpels is the difficulty in precisely aligning it on target, i.e., on the spot or along the line of the cut, during the time the operation is being performed. One proposed arrangement uses a lens system which focusses the laser beam in front of the tip of the scalpel to permit viewing the working area. This arrangement includes two light sources that project two light beams which intersect at the focal point of the laser beam, to target the beam on the spot or line to be cut. Another proposed arrangement (see U.S. Pat. No. 3,659,613) includes an eyepiece for viewing the target area, and a rotatable chopper disc for alternately passing the laser beam to the target area and the viewable light to the eyepiece. Such arrangements, however, are not entirely satisfactory with respect to the precision, and the convenience of alignment and manipulation, required by a surgeon in performing delicate surgical operations.